1. Field of the Invention
The present invention relates to a process cartridge, a method for assembling a process cartridge and an image forming apparatus containing the cartridge. The image forming apparatus may be, for example, a laser beam printer, an electrophotographic copying machine, a facsimile machine, a word processor or the like.
2. Related Background Art
In an image forming apparatus such as a printer, a latent image is formed by selectively exposing an image bearing member, which has been uniformly charged. The latent image is then visualized with toner as a toner image, which is, in turn, transferred onto a recording sheet, thereby recording an image on the recording sheet. In such an apparatus, whenever the toner is consumed or used up, new toner must be replenished. However, the toner replenishing operation is not only troublesome, but also often causes the contamination of surroundings. Further, maintenance of various elements of the apparatus must be performed periodically.
To this end, a so-called process cartridge has been proposed and put into practical use (for example, as disclosed in U.S. Pat. Nos. 3,985,436, 4,500,195, 4,540,268 and 4,627,701) wherein a photosensitive drum, a charger, a developing device, a cleaning device and the like are integrally contained in a cartridge housing which can be removably mounted to an image forming apparatus, and whereby the replenishment of toner or the exchange of parts, the service lives of which have expired can be permitted and maintenance can be facilitated.
In such a process cartridge, in some cases, an openable drum shutter is provided for covering an exposed portion of a photosensitive member to prevent the deterioration of the photosensitive member when the process cartridge is dismounted from the image forming apparatus. The drum shutter is automatically opened by engaging a link portion of the drum shutter by a cam portion of the image forming apparatus when the process cartridge is inserted into the image forming apparatus, and is automatically closed by a biasing force of a spring when the process cartridge is dismounted from the image forming apparatus.
In a process cartridge having the drum shutter, since the drum shutter is opened in opposition to the biasing force of the spring when the cartridge is inserted into the apparatus, a load is generated in a cartridge inserting direction. Since the link portion for opening the drum shutter is generally provided on a longitudinal end of the process cartridge, uniform or same loads are not applied to both longitudinal sides of the process cartridge, thereby generating play in the cartridge mounting and dismounting operation.
Other than the loading resistance due to the opening of the drum shutter during the mounting of the process cartridge, when a conductive member for grounding a photosensitive member protrudes from the longitudinal end of the process cartridge and is contacted with a contact portion of the image forming apparatus when the cartridge is inserted into the apparatus, a load is also generated by the sliding contact between the conductive member and the contact portion, thereby giving rise to the same problem as mentioned above.